1. Field of the Invention
The present invention relates to content management systems and, more specifically, to a content management system in which content and its usage rules under management of a certain content management terminal are temporarily moved to an intermediate system, and then moved back to the same content management terminal or moved to any other content management terminal.
2. Description of the Background Art
In recent years, after the progress of the technology for digital information compression and the appearance of the high-speed network infrastructure, various content distribution services have become available over the network such as the Internet. As exemplary services, there are a music distribution service for distributing music contents from Web pages, and a market information distribution service utilizing e-mails.
Generally, digital contents are easy to duplicate so that content management plays a key role especially in content distribution services which involve a billing process. Unauthorized duplication and tampering cause a huge loss to service providers and copyright holders. Japanese Patent Laid-Open Publication No. 7-131452 (1995-131452) discloses an exemplary copyright management system considering unauthorized duplication and tampering. In the content management method disclosed therein, a terminal receives encrypted content, its usage rules, and its decryption key, and after tampering detection, starts verifying the appropriateness of the usage rules. Only when the verification turns out to be completely satisfactory, the content is decrypted and outputted.
Here, the usage rules are information to limit the use of the content, and specify the number of uses, expiration date, and others. Specifying the expiration date enables the content distribution service providers to offer rental services, and setting up the usage rules enables the providers to change the price setting depending thereon, realizing the wide range of services. In view of these advantages, the content distribution services are often provided under such usage rules.
Further, recording media (hereinafter, referred to as copyright protection media), exemplified by DVDs and SD cards, incorporating a copyright protection mechanism have been recently developed, and contents recorded on such media become free from unauthorized duplication. Therefore, some service providers who offer content distribution services have started allowing distribution contents to be moved to the copyright protection media. Here, “moving the content” means an “operation of moving content together with its usage rules from A to B, and after the completion of movement, the content is not left available for A.” That is, the service providers have started allowing contents to be moved to the copyright protection media because no content is duplicated thereby.
The contents moved to the copyright protection media are available through output (reproduction) units which are specifically for the copyright protection media. This makes contents obtained from the service providers and then recorded on stay-at-home units also available through portable units, whereby content usability for users is increased.
Here, the contents temporarily moved to the copyright protection media are not always used by the output (reproduction) units specifically designed for the copyright protection media. For example, after moved to the copyright protection media, the contents may be used again by the stay-at-home units, from which those are originally moved. For use in the portable units during commuting hours and then in personal computers during office hours, the contents may be moved from the stay-at-home units to the copyright protection media, and then to the personal computers. In some other cases, the copyright protection media may be used as a mere vehicle for moving content data between stay-at-home units. The content data may be transferred to other users via the copyright protection media.
The issue here is that, during such cases, the usage rules which have been originally set to the contents may be lost. This is because the copyright protection media do not share the same usage rules. In the below, described in detail is how the usage rules are lost.
Exemplified here is a case where an e-book content purchased through an e-book distribution service A is the one to be moved. Assuming that the e-book distribution service A attaches every selling e-book content with three usage rules (expiration date, Yes or No for printing, Yes or No for content moving). The users use e-book contents purchased through receiving terminals under the usage rules coming therewith. Assuming that a user purchased an e-book content C whose usage rules are (expiration date=“Apr. 21, 2001”, Yes or No for printing=“Yes”, Yes or No for content moving=“YES”), he/she is entitled to read the purchased e-book content C at any time before Apr. 21, 2001, and is at liberty to make printouts thereof. The user is also authorized for content moving, whereby the e-book content C recorded on his/her stay-at-home unit can be moved to his/her own copyright protection medium M to read the e-book content C through an e-book reader unit.
Here, presumably, the usage rule defined by an e-book storage format F on the copyright protection medium M is only (expiration date). This tells that the format F on the copyright protection medium M is not designed with printing by the e-book reader units in mind. Thus, the user cannot make printouts of the e-book content C in the medium M by the e-book reader unit, but is at liberty to read it at any time until Apr. 21, 2001.
There occurs a problem if the user tries to move the e-book content C in the medium M to some other units (e.g., unit from which the content originally came, or other units). This is because the medium M includes no usage rule concerning Yes or No for printing. Therefore, moving the content via the medium M will resultantly lose the usage rule concerning Yes or No for printing. That is, even if a destination terminal is designed for printing of the e-book content C, no such usage rule concerning printing comes from the medium M. Therefore, the destination terminal cannot make printouts of the e-book content C.
Such a problem surely makes the users cautious and wary of moving e-book contents to the copyright protection media, and if seeing any possibility of making printouts of the contents, the users may give up reading those through portable e-book reader units. This resultantly impairs the portability and usability of the contents. This problem also arises when the copyright protection media are used as a mere vehicle for moving the content data. As a result, the portability and usability of the copyright protection media are not fully utilized, and the users will find those not worth using.
Such a problem is not particular only to the case of moving contents via the copyright protection media, and more generally, becomes apparent when the contents are moved through a system in which their usage rules are not fully defined.